The present invention relates to ligands and asymmetric catalysts using such ligands. More particularly, the invention relates to asymmetric catalysts which promote cyanosilylation such a manner that an enantiomic reaction may be selectively effected.
The asymmetric catalyst means a catalyst that can itself produce an optically active substance and can discriminate enatiomers. Various products can be obtained simply by utilizing, as starting materials or the like, various products obtained with use of the asymmetric catalysts.
Investigations are now intensively being made on asymmetric catalysts for cyanation of carbonyl compounds such as aldehydes, imines, ketones, etc. With respect to an example of chemical catalysts used, a catalyst exhibiting an enantiomer excess of around 72% at the maximum for the arylmethyl ketones has been known.
However, no practical asymmetric catalyst has not been reported for the ketones. In actual, even the above-mentioned chemical catalysts used have a problem that they cannot be applied to ethylketone (30%) or an aliphatic ketone. If an asymmetric catalyst which can act upon general ketones including ethyl ketone and the aliphatic ketones can be obtained, large quantities of useful materials required in large amounts for medical and pharmaceutical researches, such as quaternary xcex1-hydroxycarboxylic acid, quaternary xcex2-amino alcohol, etc. can be simply synthesized. Therefore, development for the effectively catalytic cyanosilylation of ketones has been eagerly awaited for a long time. However, such asymmetric catalysts have not come into existence.